New in Symfony 2.6: Support for KiB and MiB units in FileValidator

How many bytes are in 3 kilobytes? Strictly speaking, the kilo prefix always
refers to 1,000, so the answer may be 3,000 bytes. However, in some computer
science contexts, kilo is usually (and wrongly) interpreted as 1,024 so the
answer could also be 3,072 bytes.

In order to solve these issues, the IEC (International Electrotechnical Commission)
established in 1998 the binary units (Ki, Mi, Gi, etc.) to distinguish them from
the traditional units (K, M, G, etc.) For instance, the kibibyte unit refers
to 1,024 bytes, instead of the 1,000 bytes associated with the kilobyte.

As of Symfony 2.6, you can use the Ki and Mi units to set the maximum
file size of the FileValidator constraint: